I have seen the tank you are talking about I agree that flat screen design is a very bad design but one of the old floor model tv's would be great. Maybe you could just take out the insides and find a tank that would just fit inside it.

You can put a tank in a wall and ahve it protruding 2-3 inches out and then add the flatscreen to it as a frame, then u have a "flat screen fishtank" that looks deep but from the side looks like it should be flat